1. Field of the Invention
The present invention relates to rotating magnetic disk drives, and more particularly, to a method for more reliably reducing the effects of repeatable runout in the location of embedded servo sectors relative to a concentric track center.
2. Description of the Prior Art and Related Information
Repeatable runout (RRO) in a disk drive results from imperfections, with respect to a perfect circle, in the location of servo information along a track on a disk surface in the disk drive. Due to disk spindle rotation, the servo imperfections due to RRO are periodic having a fundamental frequency that is equal to the spindle rotation frequency. The RRO imperfections are relatively static over time and the effects of the RRO may be attenuated by measuring the RRO and storing RRO cancellation values for later use in a head-position servo loop to compensate for the RRO effects.
Accordingly, there exists a need for a technique for reliably storing the RRO cancellation values for significantly reducing the effects of RRO.